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Date: Thu, 14 Nov 2024 11:21:49 +0000 Message-ID: <1879585.atdPhlSkOF@rogueboard> In-Reply-To: References: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org X-Auto-Response-Suppress: DR, RN, NRN, OOF, AutoReply MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart46805127.fMDQidcC6G"; micalg="pgp-sha256"; protocol="application/pgp-signature" X-PPP-Message-ID: <173158332845.382728.6729368583990225552@cloud238.thundercloud.uk> X-PPP-Vhost: kintzios.com X-Spamd-Result: default: False [-1.51 / 999.00]; SIGNED_PGP(-2.00)[]; MID_RHS_NOT_FQDN(0.50)[]; ONCE_RECEIVED(0.20)[]; MIME_GOOD(-0.20)[multipart/signed,text/plain]; MX_GOOD(-0.01)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_TLS_ALL(0.00)[]; DMARC_POLICY_ALLOW(0.00)[kintzios.com,none]; FROM_HAS_DN(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; REPLYTO_DOM_NEQ_TO_DOM(0.00)[]; ARC_NA(0.00)[]; RCPT_COUNT_ONE(0.00)[1]; MISSING_XM_UA(0.00)[]; ASN(0.00)[asn:34931, ipnet:149.255.60.0/22, country:GB]; MIME_TRACE(0.00)[0:+,1:+,2:~]; TO_DN_NONE(0.00)[]; REPLYTO_ADDR_EQ_FROM(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_ONE(0.00)[1]; PREVIOUSLY_DELIVERED(0.00)[gentoo-user@lists.gentoo.org]; R_DKIM_NA(0.00)[]; NEURAL_HAM(-0.00)[-0.999]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_SPF_ALLOW(0.00)[+mx]; HAS_REPLYTO(0.00)[confabulate@kintzios.com] X-Rspamd-Queue-Id: 0466F1E0006 X-Rspamd-Action: no action X-Rspamd-Server: mailclean11 X-Archives-Salt: 334501b7-403e-4e74-82dc-556441433485 X-Archives-Hash: 56b9f1049b0ebf98f5e4467dbbb4f6d1 --nextPart46805127.fMDQidcC6G Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8"; protected-headers="v1" From: Michael To: gentoo-user@lists.gentoo.org Reply-To: confabulate@kintzios.com Subject: Re: [gentoo-user] Seagate hard drives with dual actuators. Date: Thu, 14 Nov 2024 11:21:49 +0000 Message-ID: <1879585.atdPhlSkOF@rogueboard> In-Reply-To: References: MIME-Version: 1.0 On Wednesday 13 November 2024 23:10:10 GMT Dale wrote: > Howdy, >=20 > One of my PVs is about 83% full. Time to add more space, soon anyway. > I try not to go past 90%. Anyway, I was looking at hard drives and > noticed something new. I think I saw one a while back but didn't look > into it at the time. I'm looking at 18TB drives, right now. Some new > Seagate drives have dual actuators. Basically, they have two sets of > heads. In theory, if circumstances are right, it could read data twice > as fast. Of course, most of the time that won't be the case but it can > happen often enough to make it get data a little faster. Even a 25% or > 30% increase gives Seagate something to brag about. Another sales tool. > Some heavy data users wouldn't mind either. >=20 > My question is this. Given they cost about $20 more, from what I've > found anyway, is it worth it? Is there a downside to this new set of > heads being added? I'm thinking a higher failure rate, more risk to > data or something like that. I think this is a fairly new thing, last > couple years or so maybe. We all know how some new things don't work out. >=20 > Just looking for thoughts and opinions, facts if someone has some. > Failure rate compared to single actuator drives if there is such data. > My searched didn't help me find anything useful. >=20 > Thanks. >=20 > Dale >=20 > :-) :-) I don't know much about these drives beyond what the OEM claims. From what= I=20 read, I can surmise the following hypotheses: These drives draw more power from your PSU and although they are filled wit= h=20 helium to mitigate against higher power/heat, they will require better cool= ing=20 at the margin than a conventional drive. Your system will use dev-libs/libaio to read the whole disk as a single SAT= A=20 drive (a SAS port will read it as two separate LUNs). The first 50% of LBA= s=20 will be accessed by the first head and the last 50% by the other head. So= =20 far, so good. Theoretically, I suspect this creates a higher probability of failure. In = the=20 hypothetical scenario of a large sequential write where both heads are writ= ing=20 data of a single file, then both heads must succeed in their write operatio= n. =20 The cumulative probability of success of head A + head B is calculated as=20 P(A=E2=8B=82B). As an example, if say the probability of a successful writ= e of each=20 head is 80%, the cumulative probability of both heads succeeding is only 64= %: 0.8 * 0.8 =3D 0.64 As long as I didn't make any glaring errors, this simplistic thought=20 experiment assumes all else being equal with a conventional single head dri= ve,=20 but it never is. The reliability of a conventional non-helium filled drive= =20 may be lower to start with. Seagate claim their Exos 2 reliability is=20 comparable to other enterprise-grade hard drives, but I don't have any real= =20 world experience to share here. I expect by the time enough reliability=20 statistics are available, the OEMs would have moved on to different drive=20 technologies. When considering buying this drive you could look at the market segment nee= ds=20 and use cases Seagate/WD could have tried to address by developing and=20 marketing this technology. These drives are for cloud storage=20 implementations, where higher IOPS, data density and speed of read/write is= =20 desired, while everything is RAID'ed and backed up. The trade off is power= =20 usage and heat. Personally, I tend to buy n-1 versions of storage solutions, for the follow= ing=20 reasons: 1. Price per GB is cheaper. 2. Any bad news and rumours about novel failing technologies or unsuitable= =20 implementations (e.g. unmarked SMRs being used in NAS) tend to spread far a= nd=20 wide over time. 3. High volume sellers start offering discounts for older models. However, I don't have a need to store the amount of data you do. Most of m= y=20 drives stay empty. Here's a 4TB spinning disk with 3 OS and 9 partitions: ~ # gdisk -l /dev/sda | grep TiB Disk /dev/sda: 7814037168 sectors, 3.6 TiB Total free space is 6986885052 sectors (3.3 TiB) HTH --nextPart46805127.fMDQidcC6G Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. 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